1. Field of the Invention
THIS INVENTION relates to a plug for use in a borehole. More particularly, the invention relates to a plug for use in a borehole and to a method of supporting materials in a borehole.
2. Description of the Related Art
UK Patent No. 2,211,587 A discloses a constriction means for use in a vertical borehole which comprises a plastics bucket which is seated in a cylindrical wall gripping means. The wall gripping means is capable of lateral expansion to grip inner sides of the borehole so that the constriction means is prevented from moving inside the borehole.
According to the invention, there is provided a plug for use in a borehole, the plug including a body member of a flexible material, the body member defining a floor portion, with a wall portion bounding and extending from the floor portion for engagement with an inner wall of the borehole for sealing the borehole.
Preferably, the body member is of a resiliently flexible material such as a suitable synthetic plastics material.
The plug may further include an attachment means carried by the body member for attaching a manipulating means to the body member to control its positioning within the borehole.
The body member may define a receptacle in which material to be supported is received, with the wall portion extending from the floor portion in a flared manner such that a rim of the wall portion bounds an opening having a greater area than that of the floor portion.
Further, one end of the wall portion may be lower than an opposed higher end, the lower end being a leading end and the higher end being a trailing end of the body member when it is inserted into the borehole, the body member defining an offset frusto-conical element so that an axis of the frusto-cone is at a predetermined angle to the vertical when the body member is lying on its rim.
The lower end and the higher end of the wall portion may each extend at an angle of between 90xc2x0 to 130xc2x0 to the floor portion.
The arrangement may be such that, when the body member rests on its floor portion, the lower end of the wall portion extends substantially vertically, or at a shallower angle to the vertical, than the higher end of the wall portion, which may flare outwardly from the floor portion at a predetermined angle to the vertical greater than that of the lower end. Instead, the lower end of the wall portion and the higher end of the wall portion may extend substantially parallel to each other such that, when the body member is viewed from the side, it is substantially trapezoidal and not frusto-conical.
At least one circumferential groove may be defined in the wall portion.
The attachment means may be carried on the wall portion at said leading end of the wall portion. The attachment means may be an opening defined in said leading end of the wall portion proximate a rim of the wall portion.
The plug may further include a manipulating means in the form of an elongate, filamentary element such as a length of string which is secured to the attachment means of the body member, the string being of a predetermined length for positioning the body member at a desired location, or depth, in the borehole.
The plug may yet further include a securing means for securing a free end of the length of string at an entrance opening or mouth of the borehole. The securing means may be in the form of an anchor which, in use, may be of a length dimension exceeding a diameter of the mouth of the borehole to overlie and rest on the substrate into which the borehole has been drilled.
The plug may also include a trailing end attachment means which is carried on the wall portion at said trailing end of the wall portion, with a recovery means in the form of a length of string being secured to the attachment means of the body member for recovery of the body member from the borehole.
In an alternative embodiment of the invention, the plug as claimed in claim 1, in which the floor portion is substantially planar.
The floor portion may have a thickness of between 0.5 mm and 30 mm.
To assist in deformation of the body member, in use, a wedge-shaped groove may be defined in the floor portion, the wedge-shaped groove increasing in depth from the leading end of the floor portion to the trailing end to impart a cloven hoof-shape to the body member, when viewed externally of the body member. Still further, the floor portion may be slightly dished to have a concave shape when viewed externally of the body member.
The invention extends also to a method of supporting materials in a borehole which includes inserting a plug into the borehole;
displacing the plug through approximately 900 and, in so doing deforming the plug to wedge it in the borehole; and
charging the materials to be supported into the borehole so that the materials are at least partially received in a receptacle defined by the plug.
The invention is now described by way of example with reference to the accompanying diagrammatic drawings.